Australian P-8A Poseidon Takes Key Role in Four-Nation Indo-Pacific Undersea Warfare Exercise.

Australia deployed a Royal Australian Air Force P-8A Poseidon alongside U.S., Japanese and South Korean submarines in a four-nation anti-submarine warfare exercise in the Western Pacific, according to details released on September 4, 2026. Conducted from August 25 to 27, the exercise strengthened allied ability to detect, track and respond to submarines across a contested maritime battlespace.

The drills integrated submarines, maritime patrol aviation and theater-level command and control, highlighting the P-8A’s role in coordinating long-range airborne anti-submarine warfare with allied naval forces. For Australia, this capability supports protection of critical sea lanes and coalition sea control as undersea warfare becomes increasingly important to Indo-Pacific deterrence.

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Australia’s deployment of a Royal Australian Air Force P-8A Poseidon alongside U.S., Japanese, and South Korean submarines during ASWEX 2026 highlights Canberra’s expanding role in high-end Indo-Pacific anti-submarine warfare, where airborne sensors, submarine operations, and allied command networks are increasingly being integrated to strengthen undersea detection, tracking, and regional sea control (Australian MoD)

On September 4, 2026, Australia has reinforced its growing role in multinational undersea warfare operations in the Indo-Pacific, deploying a Royal Australian Air Force P-8 Poseidon alongside U.S., Japanese and South Korean submarines during a sophisticated multilateral Anti-Submarine Warfare Exercise in the Western Pacific. Conducted from August 25 to 27, ASWEX integrated submarines, maritime patrol aviation and theater-level command and control within a common operational construct, demonstrating how Australia is increasingly contributing high-end airborne anti-submarine warfare capabilities to allied maritime operations. The exercise is strategically significant for Canberra because effective control of the subsurface battlespace remains fundamental to protecting maritime freedom of maneuver, securing regional sea lines of communication and supporting coalition sea control across the Indo-Pacific.

Three submarines representing the U.S. Navy, Japan Maritime Self-Defense Force and Republic of Korea Navy formed the subsurface core of ASWEX, while Australia provided the exercise's principal airborne anti-submarine warfare contribution through a Royal Australian Air Force P-8 Poseidon. A Royal Australian Navy liaison officer simultaneously supported operations from the Commander Task Force 74 Theater Undersea Warfare Commander’s Maritime Operations Center in Yokosuka, giving Australia a presence both in the tactical battlespace and within the multinational command-and-control architecture. Participating forces tested communication pathways and conducted tactical maneuvers in close proximity, including tracking exercises, simulated undersea engagements and joint water space management. Collectively, these activities exercised some of the most demanding elements of multinational submarine and maritime patrol operations: maintaining track custody, deconflicting friendly submerged forces and coordinating tactical action while preserving an accurate common undersea operational picture.

The importance of Australia’s participation extends beyond simply adding another platform to a four-nation exercise. By integrating a RAAF P-8 Poseidon with three allied submarine forces while simultaneously embedding a RAN liaison officer within the theater undersea warfare command structure, Australia connected both its airborne surveillance capability and naval command expertise to the same tactical undersea problem. The United States, Japan, South Korea and Australia operate different force structures, command relationships and national procedures, making effective integration an operational challenge in its own right. ASWEX addresses a central requirement of coalition maritime warfare: converting individually capable national assets into a coherent theater-level combat system. In any high-end Indo-Pacific contingency, hostile submarine activity would not conform to national boundaries or isolated operating areas. For Australia, the ability to exchange tactical information, coordinate water space, maintain contact continuity and rapidly integrate P-8 sensor information with allied submarines could become decisive to protecting maritime approaches and denying an adversary freedom of action beneath the surface.

The Australian P-8 contribution is particularly significant because modern anti-submarine warfare is not a submarine-versus-submarine contest but a multidomain detection and prosecution problem in which maritime patrol aircraft, submarines, surface combatants and distributed sensors contribute different elements of the find, fix, track and engagement sequence. A RAAF P-8 operating in support of three U.S. and allied submarine forces represents substantially more than airborne participation. It allows Australian crews and allied commanders to rehearse the correlation of acoustic and non-acoustic information between air and subsurface elements while maintaining positive water space management around friendly submarines. The Poseidon’s ability to cover large maritime areas makes it particularly valuable within this construct, providing an airborne layer capable of supporting wide-area submarine detection and tracking while feeding information into a broader multinational undersea picture. In operational terms, ASWEX strengthened Australia’s maritime air-undersea warfare readiness by developing the procedures required for a RAAF P-8 to function as both a sensor platform and an integrated node within a larger coalition undersea warfare architecture.

For Australia, this is where interoperability with the United States and key regional partners becomes a force multiplier rather than simply a diplomatic objective. Rear Adm. Gary Montalvo, commander of Submarine Group Seven, emphasized that operating complex undersea assets in close proximity requires absolute precision and robust communication. ASWEX directly exercised those requirements, with the RAAF P-8 required to operate effectively around multiple friendly submarines while Australian naval personnel participated in the command-and-control structure supporting the exercise. Joint water space management is particularly consequential because friendly submarines must retain stealth, survivability and tactical freedom while maritime patrol aircraft and other ASW forces operate within the same battlespace. Communications discipline, positive identification, operating-area deconfliction, tactical information exchange and common procedural understanding are prerequisites for credible multinational undersea warfare. Practicing those mechanisms gives Australian aircrew and naval commanders greater experience in integrating into a complex coalition undersea operation during crisis or conflict.

The geography behind ASWEX also gives Australia’s participation significance beyond the waters in which the exercise was conducted. Commander Submarine Group Seven directs forward-deployed combat-capable forces across the full spectrum of undersea warfare throughout the Western Pacific, Indian Ocean and Arabian Sea,  maritime regions that intersect directly with Australia’s own strategic interests and dependence on secure sea lines of communication. The operational principles rehearsed during ASWEX,  multinational submarine coordination, theater command and control, airborne ASW integration, tactical communications and joint water space management, are relevant across a maritime arc extending from Northeast Asia through Southeast Asia and into the wider Indian Ocean. For Canberra, the Western Pacific cannot be separated operationally from the maritime approaches linking Australia to Northeast Asia, the Indonesian archipelago and the Indian Ocean. Viewed strategically, Australia’s P-8 and RAN participation reflects the country’s growing role within an emerging multinational theater undersea warfare architecture capable of sustaining awareness and coordinating operations across an increasingly interconnected maritime battlespace.

ASWEX consequently demonstrates an important evolution in Australia’s contribution to the Indo-Pacific security architecture: interoperability is increasingly being developed at the tactical level where political alignment is converted into operational capability. A Royal Australian Air Force P-8 supporting three U.S. and allied submarines, a Royal Australian Navy liaison officer integrated with the Theater Undersea Warfare Commander’s Maritime Operations Center, and four nations practicing common communications and water space management represent more than individual training events. Together, they show how Australia can contribute both a sophisticated airborne anti-submarine warfare capability and personnel capable of operating within multinational theater command structures. The exercise provides a practical indication of how Australian maritime patrol aviation could support allied submarine operations during much larger and more demanding regional contingencies.

For Canberra, that represents a significant strategic capability. Australia is increasingly positioned to contribute maritime patrol aviation, undersea warfare expertise and regional operating experience to coalition operations stretching across the Indo-Pacific. The RAAF P-8 Poseidon is particularly important within that posture because its range, persistence and anti-submarine warfare mission allow Australia to contribute directly to the detection and tracking of submarines across large maritime areas while supporting allied surface and subsurface forces. Combined with Australian personnel integrated into theater-level command and control, this strengthens the country’s ability to operate as part of a networked multinational undersea force.

From the Western Pacific through Southeast Asia and into the Indian Ocean, stronger theater undersea warfare coordination can improve the resilience of Australian and allied maritime operations while creating greater uncertainty for any potential adversary seeking to exploit the opacity of the subsurface domain. ASWEX was more than a three-day anti-submarine warfare exercise for Australia. It demonstrated how the RAAF’s P-8 Poseidon and Royal Australian Navy expertise are becoming increasingly integrated into a coalition undersea warfare network designed to strengthen deterrence and preserve freedom of maneuver across a free and open Indo-Pacific.

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Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group

Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.